1. Field of the Invention
The present invention relates to a charge pump circuit, and more particularly, to a charge pump that generates a plurality output voltage according to an input voltage, and a method thereof.
2. Description of the Prior Art
A charge pump circuit is one of the most important elements in a displaying apparatus. Normally, the charge pump circuit is utilized for generating an output voltage that is higher than an input voltage of the charge pump circuit. Please refer to FIG. 1. FIG. 1 is a diagram illustrating a conventional charge pump circuit 100. The charge pump circuit 100 includes a first input switch SW1, a second input switch SW2, a first output switch SW3, a second output switch SW4, a charging capacitor C1, and a pumping capacitor C2. A node N1 of the first input switch SW1 receives the input voltage Vi, and a node N2 of the second input switch SW2 is coupled to a first ground reference voltage Vg1. The charging capacitor C1 is coupled between nodes N3 and N4, the pumping capacitor C2 is coupled between nodes N5 and N6, in which the node N5 is utilized for outputting the output voltage Vo and the node N6 is coupled to a second ground reference voltage Vg2. Furthermore, the first output switch SW3 is coupled between the nodes N3 and N5, and the second output switch SW4 is coupled between the nodes N4 and N6.
According to the conventional charge pump circuit 100, when the first input switch SW1 and the second input switch SW2 are switched on, the electric charge corresponding to the voltage difference between the input voltage Vi and the first ground reference voltage Vg1 is charged to the charging capacitor C1. Meanwhile, the first output switch SW3 and the second output switch SW4 are switched off. Then, the first output switch SW3 and the second output switch SW4 are switched on to pump the electric charge to the pumping capacitor C2. By appropriately setting the second ground reference voltage Vg2 and the capacitance of the pumping capacitor C2, the output voltage Vo having a voltage level higher than the input voltage Vi can be generated. In view of the above-mentioned conventional charge pump circuit 100, only one output voltage is generated by the group of a charging capacitor and a pumping capacitor. When a large number of output voltage need to be generated in the displaying apparatus, a large number of the group of a charging capacitor and a pumping capacitor are also required. Therefore, this will significantly increase the cost of the displaying apparatus. Therefore, utilizing a predetermined number of capacitor to generate a plurality of output voltages for lowering the cost of each charge pump circuit is an urgent problem in the field of displaying apparatus.